With current technology, continuous manufacturing processes can produce up to 900 products per minute and more. The high speeds can magnify problems of handling materials due to the materials' interaction with machine contamination, machine wear, and other typical production altering variables. In addition to the complexities existing from high speeds, most manufacturing processes consists of assembling a plurality of different elements to make a final product. As processing speeds and the number of elements required in an assembly increase, the ability to produce quality articles within their specifications becomes increasingly difficult. To manage this difficulty, sophisticated control and registration systems have been developed. U.S. Pat. Nos. 4,264,957 and 4,361,260 disclose two such systems. Many of the known systems employ the use of electrical equipment, such as computers and sensors, which require on-going maintenance and energy costs.
Friese, U.S. Pat. No. 4,816,100 and related patents, discloses a simple, yet effective, method of controlling the position of discrete sections of nonwoven materials as the sections are separated from a stock roll and further manipulated. The method consists of the following steps: perforating the material transversely to its longitudinal direction, thereby maintaining strands of material between the perforated regions; optionally stretching the strands of material; and then breaking the strands by stressing the strands of material beyond their tensile strength. By only partially separating the section of material, control is maintained prior to total separation, thereby minimizing the opportunity for the material to become skewed, or otherwise out of position as it continues through the process. The time period and locations along a continuous process between the partial and total separation is fairly unlimited.
While the invention of Friese is useful with nonwoven materials, other materials, such as apertured films may not separate as effectively. Partially severed nonwoven webs are relatively controllable during further severing. The unsevered strands of material will not elongate significantly, and the partially separated section of material remains controlled during final separation. Unfortunately, it has been discovered that more continuous webs, including apertured films, are less controllable in the process of Friese.
Thus, a need exists for simple and effective methods for controlling the separation of wide variety of materials in a continuous process.